Comb filter system and method

ABSTRACT

I describe and claim a temporal comb filtering system and method. The temporal comb filter system includes a comb filter to temporally process separated luminance and chrominance components from an image field responsive to image data from at least one other image field and a panel to display the processed components. The comb filter includes a cross-chroma detector to detect luminance information within chrominance data from a first image field responsive to chrominance data from at least one other image field and a cross-luma detector to detect chrominance information within the luminance data from the first image field responsive to the luminance data from at least one other image field.

REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Ser.No. 60/642,087 filed Jan. 5, 2005. And this application is acontinuation-in-part of prior application Ser. No. 10/833,979, filedApr. 27, 2004 now U.S. Pat. No. 7,304,688, which claims priority fromU.S. Provisional Application Ser. No. 60/472,280, filed May 20, 2003. Weincorporate all of these applications here by reference.

FIELD OF THE INVENTION

This invention relates to image processing and, more specifically, to asystem and method for temporally comb filtering a video signal.

BACKGROUND OF THE INVENTION

Composite video signals, commonly used in video broadcasts ortransmissions, contain a brightness signal (luminance, luma or Y) and acolor signal (chrominance, chroma or C), where the color signal ismodulated into a color sub-carrier and added to the brightness signalprior to transmission. To effectuate demodulation of the colorsub-carrier upon reception, receivers for color displays include a Y/Cseparator to separate luminance and chrominance components from thecomposite video signal. Y/C separators, however, often permit crosstalk,e.g., when luma is separated into the chrominance component (crosschroma) and chroma is separated into the luminance component (crossluma). The Y/C crosstalk generally degrades the quality of displayedvideo pictures.

One technique to reduce Y/C crosstalk is to separate composite videosignals according to their temporal changes using three-dimensional (3D)comb filters. Previous 3D comb filtering, however, has been confined toY/C separation, which limits its use to composite video signals andcomplicates the development of a multi-standard 3D comb filter.Furthermore, applying the 3D comb filters before the demodulation of thecolor sub-carrier requires special circuitry to detect locking of thehorizontal and chrominance frequencies. Accordingly, a need remains fora system and method for improved temporal processing of video signals.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of theinvention will become more readily apparent from the following detaileddescription of a preferred embodiment that proceeds with reference tothe following drawings.

FIG. 1 is a block diagram of a display system.

FIG. 2 is a block diagram of an embodiment of the signal processingsystem shown in FIG. 1.

FIG. 3 is a block diagram of an embodiment of the comb filter shown inFIG. 2.

FIG. 4 is a block diagram of an embodiment of the cross chroma detectorshown in FIG. 3.

FIG. 5 is a block diagram of an embodiment of the cross luma detectorshown in FIG. 3.

FIG. 6 is a block diagram of an embodiment of the interlaced motiondetector shown in FIG. 4.

FIG. 7 is a block diagram of an embodiment of the non-interlaced motiondetector shown in FIG. 4.

FIG. 8 is a block diagram of an embodiment of the conventional motiondetector shown in FIG. 4.

FIG. 9 is a block diagram of an embodiment of the field motion detectorshown in FIG. 5.

FIG. 10 is an example flowchart embodiment of a method for separatelytemporally processing luminance and chrominance components.

DESCRIPTION OF THE INVENTION

FIG. 1 is a block diagram of a system 100 _([n1]). Referring to FIG. 1,the system 100 includes a receiver 120 for receiving an analog imagedata signal 110, e.g., RGB or YP_(B)P_(R) signal, from a source 102. Thesource 102 may be a personal computer 107, a digital video disk player105, set top box (STB) 103, or any other device capable of generatingthe analog or digital image data signal 110. The receiver 120 may be ananalog-to-digital converter (ADC) or any other device capable ofreceiving an analog or digital video signal 109 from the analog imagedata 110. The receiver 120 converts the analog image data signal 110into the digital image data 109 and provides it to a controller 150. Aperson of reasonable skill in the art knows well the design andoperation of the source 102 and the receiver 120.

Likewise, a video receiver or decoder 122 may optionally decode ananalog video signal 112 from a video source 104 when the input is in thecomposite or s-video format. The video source 104 may be a videocamcorder, tape player, digital video disk (DVD) player, or any otherdevice capable of generating the analog or digital video signal 112. Thevideo source 104 may read (or play) external media 101. In anembodiment, a DVD player 104 plays the DVD 101. In another embodiment, aVHS tape player 104 plays a VHS tape 101. The decoder 122 converts theanalog video signal 112 into the digital video signal 109 and providesit to the panel controller 150. The decoder 122 is any device capable ofgenerating digital video signal 109, e.g., in Y/C or CVBS format, fromthe analog video signal 112. A person of reasonable skill in the artknows well the design and operation of the video source 104 and thevideo decoder 112.

A modem or network interface card (NIC) 124 receives data 114 from aglobal computer network 106 such as the Internet®. The data 114 may bein any format capable of transmission over the network 106. In anembodiment, the data 114 is packetized digital data. But the data 114may also be in an analog form. Likewise, the modem 124 may be a digitalor analog modem or any device capable of receiving data 114 from anetwork 106. The modem 124 provides digital video signal 109 to thepanel controller 150. A person of reasonable skill in the art knows wellthe design and operation of the network 106 and the modem/NIC 124.

A Digital Visual Interface (DVI) or high definition multimedia interface(HDMI) receiver 126 receives digital signals 116 from a digital source108. In an embodiment, the source 108 provides digital RGB signals 116to the receiver 126. The receiver 126 provides digital video signal 109to the panel controller 150. A person of reasonable skill in the artknows well the design and operation of the source 108 and the receiver126.

A tuner 128 receives a wireless signal 118 transmitted by the antenna119. The antenna 119 is any device capable of wirelessly transmitting orbroadcasting the signal 118 to the tuner 128. In an embodiment, theantenna 119 transmits a television signal 118 to the television tuner128. The tuner 128 may be any device capable of receiving a signal 118transmitted wirelessly by any other device, e.g., the antenna 119, andof generating the digital video signal 109 from the wireless signal 118.The tuner 128 provides the digital video signal 109 to the controller150. A person of reasonable skill in the art knows well the design andoperation of the antenna 119 and the tuner 128.

The digital video signal 109 may be in a variety of formats, includingcomposite or component video. Composite video describes a signal inwhich luminance, chrominance, and synchronization information aremultiplexed in the frequency, time, and amplitude domain for single wiretransmission. Component video, on the other hand, describes a system inwhich a color picture is represented by a number of video signals, eachof which carries a component of the total video information. In acomponent video device, the component video signals are processedseparately and, ideally, encoding into a composite video signal occursonly once, prior to transmission. The digital video signal 109 may be astream of digital numbers describing a continuous analog video waveformin either composite or component form. FIG. 1 describes a variety ofdevices (and manners) in which the digital video signal 109 may begenerated from an analog video signal or other sources. A person ofreasonable skill in the art should recognize other devices forgenerating the digital video signal 109 come within the scope of thepresent invention.

The controller 150 generates image data 132 and control signals 133 by_([n2])manipulating the digital video signal 109. The panel controller150 provides the image data 132 and control signals 133 to a paneldevice 160. The panel 160 includes a pixelated display that has a fixedpixel structure. Examples of pixelated displays are active and passiveLCD displays, plasma displays (PDP), field emissive displays (FED),electro-luminescent (EL) displays, micro-mirror technology displays, lowtemperature polysilicon (LTPS) displays, and the like. A person ofreasonable skill in the art should recognize that flat panel 160 may bea television, monitor, projector, personal digital assistant, and otherlike applications. Although FIG. 1 shows a panel 160, any device capableof displaying digital video signal 109 may be used into system 100.

The controller 150 includes a signal processing system 200 to processdigital video signal 109 according to temporal changes. Signalprocessing system 200 may be integrated into a monolithic integratedcircuit or hardwired using any number of discrete logic and othercomponents. Alternatively, the controller 150 may be a dedicatedprocessor system that includes a microcontroller or a microprocessor toimplement the signal processing system 200 as a software program oralgorithm.

In an embodiment, the controller 150 may scale the digital video signal109 for display by the panel 160 using a variety of techniques includingpixel replication, spatial and temporal interpolation, digital signalfiltering and processing, and the like. In another embodiment, thecontroller 150 may additionally change the resolution of the digitalvideo signal 109, changing the frame rate and/or pixel rate encoded inthe digital video signal 109. Scaling, resolution, frame, and/or pixelrate conversion, and/or color manipulation are not central to thisinvention and are not discussed in further detail.

Read-only (ROM) and random access (RAM) memories 140 and 142,respectively, are coupled to the display system controller 150 and storebitmaps, FIR filter coefficients, and the like. A person of reasonableskill in the art should recognize that the ROM and RAM memories 140 and142, respectively, may be of any type or size depending on theapplication, cost, and other system constraints. A person of reasonableskill in the art should recognize that the ROM and RAM memories 140 and142, respectively, are optional in the system 100. A person ofreasonable skill in the art should recognize that the ROM and RAMmemories 140 and 142, respectively, may be external or internal to thecontroller 150. RAM memory 142 may be a flash type memory device. Clock144 controls timing associated with various operations of the controller150.

_([n3])Embodiments of the signal processing system 200 will be explainedwith reference to FIGS. 2-10. FIG. 2 is a block diagram of an embodimentof the signal processing system 200 shown in FIG. 1. Referring to FIG.2, the signal processing system 200 includes a Y/C separator 210 toseparate the digital video signal 109 into chrominance 212 and luminance214 components and to provide the_([n4]) separated components 212 and214 to a field memory 220 and a 3D comb filer 300. Y/C separator 210 maybe a notch/bandpass filter set, a comb filter or a comb filter setimplementing 1D or 2D separation, or may include both separators andadapt between them responsive to digital video signal 109. An adaptiveY/C separator is described in U.S. patent application Ser. No.10/833,979, filed Apr. 27, 2004, which we incorporate by reference. Aperson of reasonable skill in the art knows well the design andoperation of the Y/C separator 210. Although FIG. 2 shows Y/C separator210 generating components 212 and 214 from digital video signal 109,system 200 may receive components 212 and 214 directly when digitalvideo signal 109 is a component video signal from an internal orexternal source. The processing system 200 may include a videodemodulator (not shown) to demodulate the chrominance component 212according to a sub-carrier phase and frequency, and provide thedemodulated chrominance component 212 to the field memory 220 and the 3Dcomb filter 300. In the following embodiments, the chrominance component212 is considered to be demodulated unless otherwise specified.

The field memory 220 stores one or more image fields from digital videosignal 109 separated into chrominance_([n5]) 212 and luminance 214components, and provides the stored chrominance 222 and luminance 224components to the 3D comb filter 300. Components 212 and 214 mayrepresent data, e.g., a pixel or group of pixels, within a current imagefield, while stored components 222 and 224 may represent datacorresponding to components 212 and 214 from at least one previous imagefield. Although FIG. 2 shows only one interconnect between field memory220 and 3D comb filter 300 for each stored component 222 and 224, storedcomponents from multiple image fields or multiple components within oneimage field, or both, may be provided to 3D comb filter 300concurrently. A person of reasonable skill in the art should recognizethat the field memory 220 may be of any type or size depending on theapplication, cost, and other system constraints.

The 3D comb filter 300 generates chrominance 302 and luminance 304 dataresponsive to components 212 and 214 from Y/C separator 210 and storedcomponents 222 and 224 from field memory 220. In one embodiment, 3D combfilter 300 generates data 302 and 304 by temporally processingcomponents 212 and 214 from a current image field responsive tocorresponding stored components 222 and 224 from at least one previousimage field. Alternatively, the 3D comb filter 300 generates data 302and 304 by temporally processing stored components 222 and 224 from oneimage field responsive to components 212 and 214 from a current imagefield and/or stored components 222 and 224 from a second image field.

FIG. 3 is a block diagram of an embodiment of the 3D comb filter 300shown in FIG. 2. Referring to FIG. 3, the 3D comb filter 300 reducesimperfections in Y/C separation by detecting and removing the crosstalkfrom each component and recombining the removed crosstalk with thecorresponding component. Although 3D comb filter 300 is shown to processimage data components 212 and 214 from Y/C separator 210 or directlyfrom digital video signal 109 responsive to stored components 222 and224 from field memory 220, in some embodiments 3D comb filter 300 mayprocess the stored components 222 and 224 from field memory 220responsive to image data components 212 and 214 and/or other storedcomponents 222 and 224 from the field memory 220.

The 3D comb filter 300 includes a cross-chroma detector 400 to detectcross-chroma 314, or luminance information, within chrominance component212 responsive to the stored chrominance component 222. Since the changein chrominance over two or more image fields includes image contentchanges (chrominance motion) and changes due to cross-chroma 314, thecross-chroma detector 400 may detect cross-chroma 314 by determining thechange in chrominance, estimating the chrominance motion over thefields, and reducing the change in chrominance with the estimatedchrominance motion. Alternatively, cross-chroma detector 400 may detectcross-chroma 314 within stored chrominance component 222 responsive tochrominance component 212.

The cross-chroma detector 400 generates adjusted chrominance data 312responsive to the chrominance component 212 and the stored chrominancecomponent 222. The adjusted chrominance data 312 may be generated byremoving the cross-chroma 314 from the chrominance component 212.Alternatively, cross-chroma detector 400 may generate adjustedchrominance data 312 by removing the cross-chroma 314 from the storedchrominance component 222. The cross-chroma detector 400 provides theadjusted chrominance data 312 to a cross-luma demodulator 310 and thecross-chroma 314 to a cross-chroma modulator 320.

3D comb filter 300 includes a cross-luma detector 500 to detectcross-luma 322, or chrominance information, within luminance component214 responsive to stored luminance component 224. Since the change inluminance over two or more image fields includes image content changes(luminance motion) and changes due to cross-luma 322, the cross-lumadetector 500 may estimate cross-luma 322 by determining the change inluminance, estimating luminance motion over the fields, and reducing thechange in luminance with the estimated luminance motion. Alternatively,cross-luma detector 500 detects cross-luma 322 within stored luminancecomponent 224 responsive to luminance component 214.

The cross-luma detector 500 generates adjusted luminance data 324responsive to the luminance component 214 and stored luminance component224. The adjusted luminance data 324 may be generated by removing thecross-luma 322 from the luminance component 214. Alternatively,cross-luma detector 500 may generate the adjusted luminance data 324 byremoving the cross-luma 322 from the stored luminance component 224. Thecross-luma detector 500 provides the adjusted luminance data 324 to thecross-chroma modulator 320 and the cross-luma 322 to the cross-lumademodulator 310.

The cross-luma demodulator 310 generates the chrominance data 302responsive to the adjusted chrominance data 312 and the cross-luma 322.Since the cross-luma 322 is modulated color sub-carrier, the cross-lumademodulator 310 may generate the chrominance data 302 by demodulatingthe cross-luma 322 and combining the demodulated cross-luma to theadjusted chrominace data 312. The cross-luma 322 may be demodulatedaccording to a sub-carrier phase and frequency used by the video decoder122 to demodulate the digital video signal 109.

The cross-chroma modulator 320 generates luminance data 304 responsiveto the adjusted luminance data 324 and the cross-chroma 314. Since thecross-chroma 314 is demodulated luminance information, the cross-lumamodulator 320 may generate the luminance data 304 by modulating thecross-chroma 314 and combining the modulated cross-luma to the adjustedluminance data 324. The cross-chroma 314 may be modulated according tothe sub-carrier phase and frequency used by the video decoder 122 togenerate the digital video signal 109, or used by the Y/C separator 210to separate the digital video signal 109. When the sub-carrier phase andfrequency information is not available to the 3D comb filter 300, e.g.,in component video signals demodulated externally from system 200, thecross-luma demodulator 310 and the cross-chroma modulator 320 passchrominance data 312 and luminance data 324, respectively, as thechrominance data 302 and 304. In other words, the 3D comb filter 300reduces the chrominance and luminance components 212 and 214 by amountof cross-luma 322 and cross-chroma 314 present in the image, but doesnot restore the signal to the original quality by recombining thecross-luma 322 and cross-chroma 314 with their respective components 212and 214.

3D comb filter 300 may include noise reduction capability to adjust thecross-chroma 314 and cross-luma 322 responsive to a noise measurement.Controller 150 may measure the transmission noise of digital videosignal 109, e.g., random noise, white noise, or the like, and providethe noise measurement to the signal processing system 200. A person ofreasonable skill in the art knows well methods of noise detection andmeasurement. In one implementation of noise reduction, the processingsystem 200 reduces the cross-chroma 314 and the cross-luma 322 prior tomodulation and demodulation, respectively, thus reducing the amount ofthe removed cross-chroma 314 and cross-luma 322 combined with adjustedchrominance data 312 and the adjusted luminance data 324. In anotherimplementation of noise reduction, the processing system 200 increasesthe cross-chroma 314 and the cross-luma 322 estimates according to thenoise measurements prior to generating the adjusted chrominance data 312and the adjusted luminance data 324, respectively.

FIG. 4 is a block diagram of an embodiment of the cross-chroma detector400 shown in FIG. 3. Referring to FIG. 4, cross-chroma detector 400includes a difference block 410 to determine the change 412 inchrominance over two or more image fields responsive to chrominancecomponents 212 and 222, where chrominance component 212 is from acurrent image field and stored chrominance component 222 is from one ormore previous image fields. The difference block 410 provides thechrominance change 412 to an interlaced motion detector 600 and a motionaggregator 420.

The interlaced motion detector 600 determines an interlaced chrominancemotion estimate 602 responsive to chrominance change 412 and chrominancecomponents 212 and 222, and provides the interlaced motion estimate 602to the motion aggregator 420. A non-interlaced motion detector 700determines a non-interlaced chrominance motion estimate 702 responsiveto chrominance components 212 and 222, and provides the non-interlacedmotion estimate 702 to the motion aggregator 420. A conventional motiondetector 800 determines a conventional chrominance motion estimate 802responsive to chrominance components 212 and 222, and provides theconventional motion estimate 802 to the motion aggregator 420.Embodiments of detectors 600, 700, and 800 will be discussed in greaterdetail below with reference to FIGS. 6, 7, and 8, respectively.

Motion aggregator 420 generates cross-chroma 314 responsive tochrominance change 412 and chrominance motion estimates 602, 702 and802, and provides cross-chroma 314 to cross-chroma modulator 320 (FIG.3) and difference block 430. Motion aggregator 420 may generatecross-chroma 314 by aggregating the chrominance motion estimates 602,702 and 802 into a total chrominance motion estimate and reducing thechrominance change 412 according to the total chrominance motionestimate. The aggregation may include selecting either the interlacedmotion estimate 602 or the non-interlaced motion estimate 702, andcombining the selected estimate 602 or 702 with the conventional motionestimate 802. In one embodiment, cross-chroma detector 400 may containfuzzy logic to adjust each chrominance motion estimate 602, 702 and 802prior to aggregation, where each fuzzy adjusted motion estimateindicates a level of membership within predefined fuzzy group or set.The cross-chroma detector 400 may implement the fuzzy logic incorresponding motion detectors 600, 700, and 800, in motion aggregator420, or within a distinct fuzzy logic module (not shown).

The difference block 430 generates adjusted chrominance data 312 byremoving the cross-chroma 314 from chrominance component 212.Alternatively, the difference block 430 removes the cross-chroma 314from stored chrominance component 222.

FIG. 5 is a block diagram of an embodiment of the cross-luma detector500 shown in FIG. 3. Referring to FIG. 5, cross-luma detector 500operates similarly to cross-chroma detector 400, except the cross-lumadetector 500 temporally processes luminance component 214. Because thecross-luma is caused by a portion of the color sub-carrier crossing overinto the luminance components 214 and 224, the luminance components 214and 224 may be filtered, e.g. with a high pass filter, to isolate thefrequencies near to the color sub-carrier.

Cross-luma detector 500 includes a difference block 510 to determine achange 512 in luminance over two or more image fields responsive toluminance components 214 and 224, where luminance component 214 is froma current image field and stored luminance component 224 is from one ormore previous image fields. The difference block 510 provides theluminance change 512 to a motion aggregator 540.

An edge motion detector 520 determines an edge motion estimate 522responsive to luminance components 214 and 224, and provides the edgemotion estimate 522 to the motion aggregator 540. In one embodiment,edge motion detector 520 isolates the low frequency portion of theluminance components 214 and 224 using a notch/bandpass filtercombination to determine the edge motion estimate 522.

A conventional motion detector 530 determines a conventional motionestimate 532 responsive to luminance components 214 and 224, andprovides the conventional motion estimate 532 to the motion aggregator540. In one embodiment, the conventional motion estimate 532 is thedifference between the current field luminance component 214 and storedluminance component 224 from four fields ago.

A field motion detector 900 determines a field motion estimate 902responsive to luminance components 214 and 224, and provides the fieldmotion estimate 902 to the motion aggregator 540. Embodiments of thefield motion detector 900 will be discussed in greater detail below withreference to FIG. 9.

Motion aggregator 540 generates cross-luma 322 responsive to luminancechange 512 and luminance motion estimates 522, 532 and 902, and providescross-luma 322 to cross-luma demodulator 310 (FIG. 3) and differenceblock 550. Motion aggregator 540 may generate cross-luma 322 byaggregating the luminance motion estimates 522, 532 and 902 into a totalluminance motion estimate and reducing the luminance change 512according to the total luminance motion estimate. The aggregation mayinclude selecting among or aggregating the estimates 522, 532 and 902.In one embodiment, cross-luma detector 500 may contain fuzzy logic toadjust each luminance motion estimate 522, 532 and 902 prior toaggregation, where each fuzzy adjusted motion estimate indicates a levelof membership within predefined fuzzy group or set. The cross-lumadetector 500 may implement the fuzzy logic in corresponding motiondetectors 520, 530, and 900, in motion aggregator 540, or within adistinct fuzzy logic module (not shown).

The difference block 550 generates adjusted luminance data 324 byremoving the cross-luma 322 from luminance component 214. Alternatively,the difference block 550 removes the cross-luma 322 from storedluminance component 224.

Embodiments of the cross-chroma detector 400 will be explained withreference to FIGS. 6-8. The following embodiments receive chrominancecomponent 212 as pixels from a current field PCF, and stored chrominancecomponent 222 as pixels from one field ago P1FT and P1FB, and two fieldsago P2F, where each pixel represents a chroma value in the UV plane.When the digital video signal 109 is interlaced the pixels from onefield ago P1FT and P1FB correspond to top and bottom pixels,respectively.

FIG. 6 is a block diagram of an embodiment of the interlaced motiondetector 600 shown in FIG. 4. Referring to FIG. 6, the interlaced motiondetector 600 determines the interlaced motion estimate 602 by detectingwhen diagonal features known to cause crosstalk are present in the imagedata. Since adjacent image fields of interlaced image data are notspatially cosited, interlaced motion detector 600 includes aninterpolator 610 to vertically interpolate a pixel 612 from pixels onefield ago P1FT and P1FB. Pixel 612 has a spatial position correspondingto pixels PCF and P2F. When the interlaced image data is NTSC (NationalTelevision Systems Committee), the interpolator 610 may average thepixels P1 FT or P1FB. When the interlaced image data is PAL (PhaseAlternating Line), the interpolator 610 may select one of the pixelsP1FT or P1FB. The interpolator 610 provides the vertically interpolatedpixel 612 to difference blocks 620 and 630.

The difference block 620 determines UV motion 622 between the currentfield pixel PCF and the spatially interpolated pixel 612, and providesthe UV motion determination 622 to the current field UV alignment 640and the non-linear UV motion detector 650. The UV motion determination622 may be the chrominance change between pixels PCF and 612.

The difference block 630 determines UV motion 632 between the pixel twofields ago P2F and the spatially interpolated pixel 612, and providesthe UV motion determination 632 to the previous field UV alignment 660and the non-linear UV motion detector 650. The UV motion determination632 may be the chrominance change between pixels P2F and 612.

The current field UV alignment 640 and previous field UV alignment 660align the U and the V portions of the UV motion determinations 622 and632, respectively, according to the implemented sampling standard, e.g.,a +/−1 delay for 601 style sampling, no delay for 4:4:4 sampling, or aninterpolator for other standards. UV alignments 640 and 660 maydetermine the direction of the diagonal stripes from the polarity of theU and V portions of the UV motion determinations 622 and 632 and adjustthe alignment according to the direction of the diagonal stripes. Thecurrent field UV alignment 640 and previous field UV alignment 660provide the aligned UV motion determinations 642 and 662, respectively,to interlace motion selector 680.

The non-linear UV motion detector 650 detects UV motion 652 over twoimage fields (PCF and P2F) caused by cross-chroma responsive to the UVmotion determinations 622 and 632. Since UV motion without cross-chromais typically linear, the non-linear UV motion detector 650 detects thenon-linearity of the UV motion responsive to the UV motiondeterminations 622 and 632. The non-linearity may be detected bydetermining the difference between the horizontal variance, e.g., thechange between PCF and P2F, and the vertical variance, e.g., the changebetween P1FT and P1FB. The non-linear UV motion detector 650 may performUV alignment similar to UV alignments 640 and 660 prior to detecting UVmotion 652. The non-linear UV motion detector 650 provides the UV motion652 to interlace motion selector 680.

The interlaced motion detector 600 may include a difference block 670 todetermine UV motion 672 between the pixels one field ago P1FT and P1FB,and to provide the UV motion determination 672 to interlace motionselector 680. The UV motion 672 may be the difference between the pixelsone field ago P1FT and P1FB.

The interlace motion selector 680 determines the interlace motionestimate 602 responsive to UV motion determinations 642, 652, 662, and672, and the chrominance change 412. The interlace motion selector 680may generate the interlace motion estimate 602 by selecting one of themotion determinations 642, 652, 662, and 672, by blending the motiondeterminations 642, 652, 662, and 672, or both. In one embodiment, theUV motion determination 672 may be selected as the interlace motionestimate 602 when Y/C separator 210 is a notch/bandpass filter. Since UVmotion determinations 642, 652, 662, and 672 are estimates of thecross-chroma present in the image data, interlace motion selector 680may determine the interlace motion estimate 602 by reducing thechrominance change 412, or total chrominance motion, by the selected UVmotion determination 642, 652, 662, or 672. In some embodiments, the UVmotion determinations 642, 652, 662, or 672 are converted into interlacemotion estimates prior to the selection by the interlace motion selector680.

FIG. 7 is a block diagram of an embodiment of the non-interlaced motiondetector 700 shown in FIG. 4. Referring to FIG. 7, the non-interlacedmotion detector 700 determines the non-interlaced motion estimate 702responsive to pixels PCF, P1FT, P1FB, and P2F. As opposed to theinterlaced motion detector 600, the non-interlaced motion detector 700determines the non-interlaced motion estimate 702 directly from thenon-cosited pixels PCF, P1FT, P1FB, and P2F.

Non-interlaced motion detector 700 includes difference blocks 710 and720 to determine UV motion estimates 712 and 722, respectively, from thepixels. The difference block 710 determines UV motion 712 between thepixels PCF and P1FT, and provides the UV motion determination 712 tonon-interlaced motion selector 730. The difference block 720 determinesUV motion 722 between the pixels P2F and P1FB, and provides the UVmotion determination 722 to non-interlaced motion selector 730. Althoughnon-interlaced motion detector 700 shows two difference block 710 and720, in some embodiments UV motion between other non-cosited pixels maybe determined and provided to selector 730.

The non-interlaced motion selector 730 generates the non-interlacedmotion estimate 702 responsive to the UV motion determinations 712 and722. The non-interlaced motion estimate 702 may be the UV motiondetermination 712 or 722 with the smallest absolute magnitude. In someembodiments, the non-interlaced motion selector 730 may generate thenon-interlaced motion estimate 702 responsive to low frequency luminancemotion determined in chross-luma detector 500 (FIGS. 3 and 5).

FIG. 8 is a block diagram of an embodiment of the conventional motiondetector 800 shown in FIG. 4. Referring to FIG. 8, the conventionalmotion detector 800 determines the conventional chrominance motionestimate 802 responsive to pixels from the current field PCF, pixelsfrom two fields ago P2F, and pixels from four fields ago P4F.

The conventional motion detector 800 includes a NTSC detector 810 togenerate a NTSC conventional motion estimate 812 responsive to pixelsPCF and P4F. The NTSC conventional motion estimate 812 may be the changein chrominance between pixels PCF and P4F. The NTSC detector 810provides the NTSC conventional motion estimate 812 to conventionalmotion selector 830.

A PAL detector 820 generates a PAL conventional motion estimate 822responsive to pixels PCF, P2F, and P4F. The PAL conventional motionestimate 822 may be the sum of the chrominance change between pixels PCFand P4F, and the chrominance change between pixel P2F and the average ofpixels PCF and P4F. Due sub-carrier phase shifts every two image fieldsin a PAL standard, the PAL detector 820 may perform UV alignment duringthe generation of the PAL conventional motion estimate 822. The PALdetector 820 provides the PAL conventional motion estimate 822 toconventional motion selector 830. Although FIG. 8 shows PAL detector 820generating the PAL conventional motion estimate 822 with pixels overfour image fields, in some embodiments a six-field conventionalchrominance motion approach is advantageous. The conventional motionselector 830 determines the conventional motion estimate 802 byselecting between the NTSC conventional motion estimate 812 and the PALconventional motion estimate 822.

FIG. 9 is a block diagram of an embodiment of the field motion detector900 shown in FIG. 5. The following embodiments receive luminancecomponent 214 as pixels from a current field PCF, and stored luminancecomponent 224 as pixels from one field ago P1FT and P1FB, and two fieldsago P2F, where each pixel represents a luminance value. When the digitalvideo signal 109 is interlaced the pixels from one field ago P1FT andP1FB correspond to top and bottom pixels, respectively.

Referring to FIG. 9, field motion detector 900 includes a plurality ofdifference blocks 910, 920, 930, and 940 to determine differences 912,922, 932, and 942, respectively. Difference block 910 determinesdifference 912 responsive to pixels PCF and P1FT. When digital videosignal 109 is a PAL signal, difference block 910 may determinedifference 912 according to (P1FT+P2F−PCF−P4F)/2, where P4F represents apixel from four fields ago. Difference block 920 determines difference922 responsive to pixels PCF and P1FB. Difference block 930 determinesdifference 932 responsive to pixels P2F and P1FB. When digital videosignal 109 is a PAL signal, difference block 930 may substitute pixelP2F with pixel P4F. Difference block 940 determines difference 942responsive to pixels P2F and P1FT. Difference blocks 910, 920, 930, and940 provide the corresponding differences 912, 922, 932, and 942 to afiled motion aggregator 950.

The field motion aggregator 950 determines the field motion estimate 902responsive to differences 912, 922, 932, and 942. In one embodiment, thefield motion aggregator 950 determines the field motion estimate 902 byselecting the minimum absolute value of differences 912, 922, 932, or942. Since the differences 912, 922, 932, and 942 assume there is novertical change in cross-luma, field motion detector 900 may determineseveral other motion estimates that take into account verticallychanging cross-luma. For instance, field motion detector 900 mayestimate field motion according to high frequency content in theprevious field (pixels P1FT and P1FB), or by limiting the field motionestimate to the difference between pixels PCF and P2F reduced by thedifference between pixels P1 FT and P1FB. Alternatively, the fieldmotion may be estimated based on the ratios of adjacent pixels from theprevious field (P1 FT) and the current field (PCF). Equation 1 shows theratios of adjacent pixels with no field motion, where the pixel index iindicates the location of the pixels within the image frame.P1FT _(i) /PCF _(i) =P1FT _(i+1) /PCF _(i+1)  Equation 1When field motion is present, however, Equation 1 may be rearranged todetermine an estimate of the field motion, as shown in Equation 2.Estimate of Field Motion=(P1FT _(i) *PCF _(i+1))−(P1FT _(i+1) *PCF_(i))  Equation 2The field motion detector 900 may provide any combination of thesemotion estimates to field motion aggregator 950, where the field motionaggregator 950 may select between them and the differences 912, 922,932, and 942 to determine the field motion estimate 902.

FIG. 10 is an example flowchart 1000 of a method embodiment foroperating 3D comb filter 300. Referring to FIG. 10, the 3D comb filter300 receives separated luminance and chrominance components from two ormore image fields at block 1010. The 3D comb filter 300 detectscross-chroma, or luminance information, within a chrominance componentfrom one of the image fields responsive to the at least one chrominancecomponent the other image fields at block 1020 and reduces thechrominance component according to the detected cross-chroma at block1030. The cross-chroma may be detected by determining a difference inthe chrominance between two or more of the image fields, estimatingchrominance motion due to image content changes over the image fields,and reducing the difference in the chrominance by the estimatedchrominance motion. In some embodiments, the detected cross-chroma maybe modified in response to a noise measurement prior to the reduction atblock 1030.

The 3D comb filter 300 detects cross-luma, or chrominance information,within a luminance component from one of the image fields responsive toat least one luminance component from the other image fields at block1040 and reduces the luminance component according to the detectedcross-luma at block 1050. The cross-luma may be detected by determininga difference in the luminance between two or more of the image fields,estimating luminance motion due to image content changes over the imagefields, and reducing the difference in the luminance by the estimatedluminance motion. In some embodiments, the detected cross-luma may bemodified in response to a noise measurement prior to the reduction atblock 1050.

According to a next block 1060, the 3D comb filter 300 modulates thedetected cross-chroma and demodulates the detected cross-luma. Thedetected cross-chroma and cross-luma may be modified responsive to anoise measurement prior the execution of block 1060. Although block 1060is shown as being performed subsequent to blocks 1040 and 1050, theirorder of operation may be concurrent or reversed. The 3D comb filter 300combines the demodulated cross-luma with the reduced chrominancecomponent at block 1070 and combines the modulated cross-chroma with thereduced luminance component at block 1080.

Having illustrated and described the principles of our invention, itshould be readily apparent to those skilled in the art that theinvention may be modified in arrangement and detail without departingfrom such principles. I claim all modifications coming within the spiritand scope of the accompanying claims.

1. A device comprising: a cross-chroma detector to detect luminanceinformation within chrominance data from a first image field responsiveto chrominance data from at least one other image field, where thecross-chroma detector is adapted to reduce the chrominance data from thefirst image field according to the detected luminance information: across-luma detector to detect chrominance information within theluminance data from the first image field responsive to the luminancedata from at least one other image field; and a cross-luma demodulatorto demodulate the chrominance information and to combine the demodulatedchrominance information with the reduced chrominance data.
 2. The deviceof claim 1 comprising a noise reducer to reduce the chrominanceinformation prior to demodulation responsive to a noise measurement. 3.The device of claim 1 where the cross-chroma detector is adapted toincrease the detected luminance information prior to the reductionresponsive to a noise measurement.
 4. A device comprising: across-chroma detector to detect luminance information within chrominancedata from a first image field responsive to chrominance data from atleast one other image field, where the cross-chroma detector is adaptedto determine a difference in chrominance data between the first imagefield and a second image field; estimate chrominance motion responsiveto chrominance data from at least the first and second image fields; anddetect the luminance information responsive to the difference and thechrominance motion; and a cross-luma detector to detect chrominanceinformation within the luminance data from the first image fieldresponsive to the luminance data from at least one other image field,where the cross-chroma detector is adapted to estimate the chrominancemotion using fuzzy logic.
 5. A device comprising: a cross-chromadetector to detect luminance information within chrominance data from afirst image field responsive to chrominance data from at least one otherimage field; a cross-luma detector to detect chrominance informationwithin the luminance data from the first image field responsive to theluminance data from at least one other image field, where the cross-lumadetector is adapted to reduce the luminance data from the first imagefield according to the detected chrominance information; and across-chroma modulator to modulate the luminance information and tocombine the modulated luminance information with the reduced luminancedata.
 6. The device of claim 5 comprising a noise reducer to reduce theluminance information prior to modulation responsive to a noisemeasurement.
 7. The device of claim 6 where the cross-luma detector isadapted to increase the detected chrominance information prior to thereduction responsive to a noise measurement.
 8. A device comprising: across-chroma detector to detect luminance information within chrominancedata from a first image field responsive to chrominance data from atleast one other image field; and a cross-luma detector to detectchrominance information within the luminance data from the first imagefield responsive to the luminance data from at least one other imagefield, where the cross-luma detector is adapted to determine adifference in luminance data between the first image field and a secondimage field; estimate luminance motion responsive to luminance data fromat least the first and second image fields, where the cross-lumadetector is adapted to estimate the luminance motion using fuzzy logic;and detect the chrominance information responsive to the difference andthe luminance motion.
 9. A device comprising: means to detect luminanceinformation within chrominance data from a first image field responsiveto chrominance data from at least one other image field, where the meansto detect luminance information is adapted to reduce the chrominancedata from the first image field according to the detected luminanceinformation; means to detect chrominance information within theluminance data from the first image field responsive to the luminancedata from at least one other image field; means to demodulate thechrominance information; and means to combine the demodulatedchrominance information with the reduced chrominance data.
 10. Thedevice of claim 9 comprising means to reduce the chrominance informationprior to demodulation responsive to a noise measurement.
 11. The deviceof claim 9 where the means to detect luminance information is adapted toincrease the detected luminance information prior to the reductionresponsive to a noise measurement.
 12. A device comprising: means todetect luminance information within chrominance data from a first imagefield responsive to chrominance data from at least one other imagefield; means to detect chrominance information within the luminance datafrom the first image field responsive to the luminance data from atleast one other image field; means to determine a difference inchrominance data between the first image field and a second image field;means to estimate chrominance motion responsive to chrominance data fromat least the first and second image fields, where the means to estimateis adapted to estimate the chrominance motion using fuzzy logic; andmeans to detect the luminance information responsive to the differenceand the chrominance motion.
 13. A device comprising: means to detectluminance information within chrominance data from a first image fieldresponsive to chrominance data from at least one other image field;means to detect chrominance information within the luminance data fromthe first image field responsive to the luminance data from at least oneother image field, where the means to detect chrominance information isadapted to reduce the luminance data from the first image fieldaccording to the detected chrominance information; means to modulate theluminance information; and means to combine the modulated luminanceinformation with the reduced luminance data.
 14. The device of claim 13comprising means to reduce the luminance information prior to modulationresponsive to a noise measurement.
 15. The device of claim 13 where themeans to detect chrominance information is adapted to increase thedetected chrominance information prior to the reduction responsive to anoise measurement.
 16. A device comprising: means to detect luminanceinformation within chrominance data from a first image field responsiveto chrominance data from at least one other image field; means to detectchrominance information within the luminance data from the first imagefield responsive to the luminance data from at least one other imagefield; means to determine a difference in luminance data between thefirst image field and a second image field; means to estimate luminancemotion responsive to luminance data from at least the first and secondimage fields, where the means to estimate is adapted to estimate theluminance motion using fuzzy logic; and means to detect the chrominanceinformation responsive to the difference and the luminance motion.
 17. Amethod comprising: detecting luminance information within chrominancedata from a first image field responsive chrominance data from at leastone other image field; detecting chrominance information within theluminance component from the first image field responsive luminance datafrom at least one other image field; reducing the chrominance data fromthe first image field according to the luminance information; reducingthe luminance data from the first image field according to thechrominance information; demodulating the chrominance information; andcombining the demodulated chrominance information with the reducedchrominance data.
 18. The method of claim 17 comprising reducing thechrominance information prior to the demodulating responsive to a noisemeasurement.
 19. The method of claim 17 comprising modulating theluminance information; and combining the modulated luminance informationand the reduced luminance data.
 20. The method of claim 19 comprisingreducing the luminance information prior to the modulating responsive toa noise measurement.
 21. The method of claim 17 comprising increasingthe detected luminance information prior to the reducing responsive to anoise measurement.
 22. The method of claim 17 comprising increasing thedetected chrominance information prior to the reducing responsive to anoise measurement.